Abstract: The invention relates to a reactor for UV radiation for the disinfection of liquids comprising at least one high or medium pressure UV emitter (1) arranged coaxially inside a protective sheath (2) transparent to UV, the assembly formed by the emitter and the sheath being located coaxially inside a tubular shell (3) whose internal face reflects at least 30% of the incident UV at 250 to 260 nm coming from the emitter (1), the liquid to be treated transiting according to a flow pipe in an active chamber (4) defined by the internal face of the shell (3) and the external face of the sheath (2), the reactor being characterized in that it is connected to washing means (30) of the active chamber (4) including means making it possible to make a cleaning liquid circulate in the active chamber (4) and air injection means (8) provided upstream from the active chamber (5) making it possible to improve the turbulence of the cleaning liquid during washing.